Dynamic Lun Resizing in a Replication Environment

1. A method for dynamically changing the size of a replication Logical Unite (LU) in a replication based environment, the replication environment having a production site and a replication site, the production site having a production LU, the replication site having a journal and the replication LU, the method comprising: changing the LU size on the production site based on a request to change the size of the LU on the production site; determining on the replication site that the LU on the production site has changed size; determining whether it is possible to change the size of the replication LU; wherein the determining whether it is possible the change the size of the LU includes accommodating applications that are dependent on the size of a LU to which the applications interact; wherein the change in the size of the replication LU accommodates the replication LU to be changed to different sizes based on production LUN sizes in a protection window of the replication based environment; wherein a protection window is a period of time for which data of the production site is accessible using the replication LU and the journal; based on a negative determination and in response to a request for the replication LU pausing replication and based on a positive determination, changing or faking the size of the replication LU; wherein changing the replication LU size includes marking in the journal the time replication LU changed and the new size of the replication LU; wherein when faking the LU size the replication site presents a faked replication LU with a different size than the replication LU.

2. The method of claim 1 wherein the change is a request to increase the size of the production LU.

3. The method of claim 2 further comprising: moving the splitter to marking mode.

4. The method of claim 2 further comprising: determining if there are applications replicated that are dependent on the size of the LU; based a positive determination, performing application pre-LU increase activity; and performing, based on the positive determination, post-LU increase activity.

5. The method of claim 2 further comprising: determining if the production and replication LU are identical in the increase area of the LU; based on a determination that the LUs are not identical, marking the new areas of the replication LU as dirty.

6. The method of claim 2 further comprising: determining if the production and replication LUs are thin LUs; and based on a negative determination marking area as dirty in a delta marking stream.

7. The method of claim 1 wherein the request is a request to decrease the size of the LU.

8. The method of claim 7 further comprising: performing application LU pre-decrease work; and performing application post LU increase work.

9. The method of claim 7 further comprising: scanning the journal to determine the maximum size of the LU in the journal; determining if the maximum size of the LU in the journal is less than replication LU size; and based on a positive determination, reducing the size of the replication LUN.

10. The method of claim 7 wherein a splitter intercepts the LU decrease request and further comprising: moving a splitter to marking mode.

11. The method of claim 1 wherein the determining of a change of the production site is based on a notification sent to the replication protection appliance.

12. The method of claim 1 wherein the determining of a change on the production site is based on a periodic check of the LU sizes and wherein, based on a determination of a change, snapshots of invalid size in the journal marked as invalid.

13. The method of claim 1 , wherein a change in the size of the LU on the production site is recorded in the journal on the replication site.

14. A system for dynamically changing the size of a replication Logical Unite (LU) in a replication based environment, the system comprising: a production site having a production LU; a replication site having a journal and a replication LU; computer-executable logic operating in memory, wherein the computer-executable program code is configured for execution across one or more processors of the following: changing the LU size on the production site based on a request to change the size of the LUN on the production site: determining on the replication site that the LU on the production site has changed size; determining whether it is possible to change the size of the replication LU; wherein the determining whether it is possible the change the size of the LU includes accommodating applications that are dependent on the size of a LU to which the applications interact; wherein the change in the size of the replication LU accommodates the replication LU to be changed to different sizes based on production LUN sizes in a protection window of the replication based environment wherein a protection window is a period of time for which data of the production site is accessible using the replication LU and the journal; based on a negative determination and in response to a request for the replication LU, pausing replication and based on a positive determination, changing or faking the size of the replication LU; wherein changing the replication LU size includes marking in the journal the time replication LU changed and the new size of the replication LU; wherein when faking the LU size the replication site presents a faked replication LU with a different size than the replication LU.

15. The system of claim 14 wherein the change is a request to increase the size of the production LU.

16. The system of claim 14 the computer-executable logic further comprising: determining if there are applications replicated that are dependent on the size of the LUN; based a positive determination, performing application pre-LU increase activity; and performing, based on the positive determination, post-LU increase activity.

17. The system of claim 14 wherein the request is a request to decrease the size of the LU.

18. A computer program product comprising: a non-transitory computer readable medium encoded with computer executable program code for dynamically changing the size of a replication Logical Unite (LU) in a replication based environment, the replication environment having a production site and a replication site, the production site having a production LU, the replication site having a journal and a replication LU, the code enabling: changing the LU size on the production site based on a request to change the size of the LU on the production site; determining on the replication site that the LU on the production site has changed size; determining whether it is possible to change the size of the replication LU; wherein the determining whether it is possible the change the size of the LU includes accommodating applications that are dependent on the size of a LU to which the applications interact; wherein the change in the size of the replication LU accommodates the replication LU to be changed to different sizes based on production LUN sizes in a protection window of the replication based environment; wherein a protection window is a period of time for which data of the production site is accessible using the replication LU and the journal; based on a negative determination and in response to a request for the replication LUN, pausing replication; and based on a positive determination, changing or faking the size of the replication LU; wherein changing the replication LU size includes marking in the journal the time replication LU changed and the new size of the replication LU; wherein when faking the LU size the replication site presents a faked replication LU with a different size than the replication LU.

19. The computer program product of claim 18 wherein the request is a request to decrease the size of the LU.

20. The computer program product of claim 18 wherein the change is a request to increase the size of the production LU.